OK let`s determine what LR is. LR is rock that is teeming with nitrifying bacteria that helps your cycle along. If you was to look at a piece of LR and a piece that was not live then you would not be able to tell the difference. But if you were to have a tank of LR vs a tank of rock that was not live you would be able to tell the difference as one tank would cycle and the other one would not be.

People think that the other stuff that comes with the LR is what makes it live, Well the other things, the algae, the crabs, snails, sea urchins, starfish... the list goes on are just "Hitch hikers". It is the bacteria let Mike stated that is the only factor to making the rock live. Now having the choice between a plain rock that someone says is live and a rock that looks full of hitch hikers I would pick the one with the hitch hikers any day. IMO